Experts Not Rattled About Drugs in Drinking Water

Lots of people lunged for bottled water after they were told last month that tap water in many U.S. cities contains traces of pharmaceuticals.

"They wanted five-gallon bottles, half-liter cases, anything that wasn't municipal water," said Jennifer Brandon, who was taking phone orders for home-delivered Deer Park water.
Responding to the public alarm, Sens. Barbara Boxer, D-Calif., and Frank Lautenberg, D-N.J., called for a hearing on the federal response to drugs in drinking water, scheduled for Tuesday.
Despite the sudden clamor, however, many water-quality researchers kept doing what they had done for years about contaminants in tap water: nothing. They kept drinking local tap or well water, a half-dozen of them said.

For one thing, they know bottled water is less-regulated than are municipal supplies.
There are reasons to worry about the safety of drinking water. Contaminants commonly found in drinking water include traces of pesticides, herbicides, flame retardants, DEET, mosquito repellent, aircraft de-icers, lead, arsenic, mercury and esters, ketones and other chemicals found in personal-care products. Not to mention additives in toothpaste meant to retard gum and tooth disease.

So why are experts relatively unfazed?

Here are some reasons:

• Improved detection technology means that we're concerned about levels of contamination that were undetectable in years past.

In the 1970s, the best detection technology picked up compounds at concentrations of one part per million. Today, concentrations of one part per trillion or even quadrillion are detectable.
With each zero of added sensitivity, myriad other chemicals are evident in water, said Christian Daughton, a research scientist at the Environmental Protection Agency's (EPA) National Exposure Research Laboratory in Las Vegas. Among them are many of the drugs now reported in drinking water.

• Even poisons are not always toxic.

Toxicology's most basic principle, researchers said, is the maxim that "the dose makes the poison." One margarita is fine for most people, in other words, but 10 could be fatal, depending on vulnerability and timing.

Toxicologists apply this principle to all poisons, but the public doesn't, according to a landmark 1991 study that examined differences in how the two groups regard risks. Its lead author was University of Oregon psychology professor Paul Slovic, founder of Decision Research, a think tank for risk assessment in Eugene, Ore.

According to Slovic, people take an "all-or-none" view of toxicity when it comes to unwanted exposures.

"What's critical to understand is that it's the dose that's important," Daughton said. "Just because a toxic substance is around, doesn't mean you're exposed to it. Your body has to come in contact with it. Your body has to absorb it. Your exposure has to be of some duration and during a critical period of time."

• Effects on animals may not predict effects on humans.

In Slovic's study, two-thirds of laypeople believed a substance that causes cancer in animals is reasonably sure to cause cancer in humans. (Six in every 10 toxicologists disagreed.)
In the case of drugs in water, reproduction in fin- and shellfish and amphibians seems to be the most affected, and the suspected culprits are natural and synthetic forms of the female hormone estrogen and substances that mimic them. In a widely cited experiment, fish in an otherwise pristine Canadian lake lost reproductive vitality when exposed to less than six parts per trillion of a commonly used synthetic form of estrogen.

The findings "raise a red flag" about other effects these drugs may be having on wildlife and possible risks to humans, said Karen Kidd, an environmental toxicologist at the University of New Brunswick's Canadian Rivers Institute who led the study.

But it is important to realize, Kidd said, that estrogens rarely are found in drinking water. Moreover, one reason fish are affected is because they're always taking up compounds through their gills. Hence, "they're getting exposed to more drugs than the average human would be from drinking water," she said.

No research has found a hazard to humans from estrogen or any other pharmaceutical in drinking water, Kidd and others noted, and Kidd said she continues to drink tap water.

• Scientists understand big numbers and use them to gauge risk. Most other people get lost in the zeros.

"There's no evolutionary reason for them to understand very big or very small numbers," said Ellen Peters, a colleague of Slovic's at the University of Oregon and at Decision Research.
When faced with a probability like one chance in a million, Peters and others said, most people glom onto the "one" and exaggerate its importance.

• Most people think irrationally about risks.

David Ropeik, a risk-communication consultant in Boston, said people feel less threatened by health risks that they choose, such as smoking, than by risks imposed on them, such as contaminated drinking water. They accept familiar risks, such as riding a bicycle, more than risks that surprise them. They also tolerate visible risks, such as choppy seas, better than invisible ones, Ropeik said. Drugs in drinking water earn mistrust on all counts.